Make scrypt.maxPending a config option.

This also renames some internal uses of "max_pending" to match the
prevailing capitalization style.

config/config.js

@@ -146,6 +146,13 @@ module.exports = function (fs, path, url, convict) {
         env: 'TOOBUSY_MAX_LAG'
       }
     },
+    scrypt: {
+      maxPending: {
+        doc: "Max number of scrypt hash operations that can be pending",
+        default: 0,
+        env: 'SCRYPT_MAX_PENDING'
+      }
+    },
     i18n: {
       defaultLanguage: {
         format: String,

crypto/scrypt.js

@@ -6,8 +6,8 @@ var P = require('../promise')
 var scrypt_hash = require('scrypt-hash')
  
 // The maximum numer of hash operations allowed concurrently.
-// This can be customized by setting the `max_pending` attribute
-// on the exported object.
+// This can be customized by setting the `maxPending` attribute on the
+// exported object, or by setting the `scrypt.maxPending` config option.
 const DEFAULT_MAX_PENDING = 100
 
 module.exports = function(log, config) {
@@ -15,9 +15,12 @@ module.exports = function(log, config) {
   var scrypt = {
     hash: hash,
     // The current number of hash operations in progress.
-    num_pending: 0,
-     // The maximum number of hash operations that may be in progress.
-    max_pending: DEFAULT_MAX_PENDING
+    numPending: 0,
+    // The maximum number of hash operations that may be in progress.
+    maxPending: DEFAULT_MAX_PENDING
+  }
+  if (config.scrypt && config.scrypt.hasOwnProperty("maxPending")) {
+    scrypt.maxPending = config.scrypt.maxPending
   }
 
   /**  hash - Creates an scrypt hash asynchronously
@@ -28,13 +31,13 @@ module.exports = function(log, config) {
    */
   function hash(input, salt, N, r, p, len) {
     var d = P.defer()
-    if (scrypt.max_pending > 0 && scrypt.num_pending > scrypt.max_pending) {
+    if (scrypt.maxPending > 0 && scrypt.numPending > scrypt.maxPending) {
       d.reject(new Error('too many pending scrypt hashes'))
     } else {
-      scrypt.num_pending += 1
+      scrypt.numPending += 1
       scrypt_hash(input, salt, N, r, p, len,
         function (err, hash) {
-          scrypt.num_pending -= 1
+          scrypt.numPending -= 1
           return err ? d.reject(err) : d.resolve(hash.toString('hex'))
         }
       )

test/local/scrypt_tests.js

@@ -5,7 +5,7 @@
 var test = require('../ptaptest')
 var promise = require('../../promise')
 var log = {}
-var config = {}
+var config = { scrypt: { maxPending: 5 } }
 
 var scrypt = require('../../crypto/scrypt')(log, config)
 
@@ -29,16 +29,14 @@ test(
   function (t) {
     var K1 = Buffer('f84913e3d8e6d624689d0a3e9678ac8dcc79d2c2f3d9641488cd9d6ef6cd83dd', 'hex')
     var salt = Buffer('identity.mozilla.com/picl/v1/scrypt')
-    // Set a lower max_pending so the test runs quicker.
-    var orig_max_pending = scrypt.max_pending;
-    scrypt.max_pending = 5;
-    // Send many concurent requests.
+    // Check the we're using the lower maxPending setting from config.
+    t.equal(scrypt.maxPending, 5, 'maxPending is correctly set from config')
+    // Send many concurrent requests.
     // Not yielding the event loop ensures they will pile up quickly.
     var promises = [];
     for (var i = 0; i < 10; i++) {
       promises.push(scrypt.hash(K1, salt, 65536, 8, 1, 32))
     }
-    scrypt.max_pending = orig_max_pending;
     return promise.all(promises).then(
       function () {
         t.fail('too many pending scrypt hashes were allowed')